For most of Thursday night’s debate, former President Donald J. Trump verbally pummeled President Biden, painting his political opponent as an ineffective leader with a torrent of attacks that were frequently false, lacked context or were vague enough to be misleading.

Mr. Trump went directly after Mr. Biden’s personal character, calling him “weak” and little respected by global leaders who were “laughing” at him.

He tried to accuse Mr. Biden of corruption, dubbing the president as a “Manchurian candidate” who was “paid by China,” a nod to frequent accusations of undue influence for which there is no evidence.

He directly blamed Mr. Biden for a wave of immigrants “coming in and killing our citizens at a level we’ve never” seen, a hyperbolic claim that is not backed up by available statistics.

And in a wild misrepresentation of facts, Mr. Trump claimed falsely that Mr. Biden “encouraged” Russia to attack Ukraine, even though Mr. Biden has consistently tried to rally support for Ukraine and his administration took active steps to warn President Vladimir V. Putin of Russia not to invade.

Mr. Trump’s remarks during the debate were not substantially different from the way he typically inveighs against Mr. Biden during his rallies, where he depicts the president as a leader who is somehow both bumbling and corrupt as he steers the country to ruin.

But the barrage of attacks during the debate was particularly striking given that Mr. Biden was standing mere feet away from him, unable to interrupt or effectively challenge Mr. Trump because of debate rules that kept his microphone muted.

And as the debate’s moderators, the CNN anchors Jake Tapper and Dana Bash, focused on keeping the peace, they did not even try to fact-check Mr. Trump’s assertions, allowing them to stand unchallenged.

Mr. Biden got in a few licks, including some of the debate’s more memorable moments. He said Mr. Trump had the “morals of an alley cat” and accused him of having sex with a porn star while his wife was pregnant.

But by and large, Mr. Biden was on the defensive from the get-go in the face of a steady stream of insults, false characterizations and attacks from Mr. Trump.

Seizing on Mr. Biden’s halting speech early in the debate, Mr. Trump pounced at one moment when Mr. Biden trailed off, saying: “I really don’t know what he said at the end of that sentence. I don’t think he knows what he said, either.”

But Mr. Trump’s most forceful attacks surrounded immigration, an issue that animated his successful 2016 campaign and that he has tried to put at the center of his bid to return to the White House.

The former president invoked the idea of “Biden migrant crime,” claiming that Mr. Biden’s lax border policy had allowed terrorists and criminals to cross the border illegally.

Mr. Trump accused his successor of “ridiculous, insane and very stupid policies” that fostered a crime wave, pointing to high-profile killings that involved immigrants. He vaguely accused Mr. Biden of killing “so many at our border” by not curbing the surge of migrants, an assertion that he did not back up with statistics.

Experts have said that those heavily publicized cases do not represent a broader trend. Studies have concluded that immigration does not push up crime rates.

Mr. Trump also went directly after Mr. Biden’s profile on the world stage. He argued that Mr. Putin was “laughing at” the president’s leadership and at his failure to secure the release of Evan Gershkovich, the Wall Street Journal reporter detained in Russia on an espionage charge that American officials vehemently deny.

”Our whole country is exploding because they don’t respect you,” Mr. Trump told Mr. Biden.

He extended those criticisms to the military, arguing that “our veterans and our soldiers can’t stand” the president. (Mr. Trump, while in office, reportedly denigrated senior American military officials.)

In repeating his frequent assertions that Mr. Biden is corrupt, Mr. Trump revived his accusations that Mr. Biden improperly received payments from a Chinese energy company associated with his son Hunter and his brother James. There is no evidence that any portion of those payments — which started after Mr. Biden left the vice presidency — went to the president.

But Mr. Trump also directly attacked Hunter Biden, who was found guilty this month on three felony counts related to his buying a gun while grappling with drug addiction. He called Hunter “a convicted felon at a very high level.”

Mr. Trump was convicted last month on 34 felony charges in Manhattan related to hush-money payments to a porn star.